The incidence of melanoma in the United States has increased between 1975 and 2010 with an estimated 76,100 new cases in 2014.1 While reasons behind this are controversial, increased recreational exposure to ultraviolet radiation is believed to be an important factor.2 Although most patients present at an early stage, some present with metastatic disease. The clinical presentation of metastatic melanoma is variable and depends on disease site, burden, and systemic effects. Diffuse melanosis is a rare manifestation of metastatic melanoma that is characterized by diffuse slate-gray discoloration of the skin and mucous membranes as a result of pigment deposition and is associated with poor prognosis.3 Here, we present a rare case of metastatic melanoma with diffuse melanosis that was initially diagnosed as disseminated sporotrichosis based on a false-positive serologic test and discuss the possible mechanism behind this observation.
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